Application of neuropsychological methods in research on the long-term consequences of childhood neurological diseases represents a new and promising advance in behavioral medicine. The purpose of the proposed investigation is to apply these methods to the study of the morbidity associated with Haemophilus influenzae type-b (Hib) meningitis. Although morbidity may affect as many as 50% of the survivors of this disease, morbidity has not as yet been studied using population samplying techniques and comprehensive assessments of neuropsychological skills, academic achievement, and behavioral and social factors. The possibility that sequelae may vary according to how old the child is at the time of testing has also been ignored. Without more complete study of developmental outcomes post-meningitis, it will be difficult to gauge the full implications of this public health problem, to make future decisions regarding preventative immunizations, or to discover more about prognostic medical and social factors. To address this issue, we will compare three age-based cohorts of post-meningitis children to their siblings on measures of neuropsychological skill, intelligence, academic achievement, and behavioral-adaptational functioning. Hearing will be screened and those children who fail screening will be given audiological examinations. Medical records and histories from parents will provide information on neurological sequelae and health status. To study outcome prospectively, the post-meningitis children will be evaluated for three successive years. Information on the acute-phase illness and on social and family variables will be collected to determine the factors that place children at greatest risk for sequelae. Hypotheses to be tested are as follows: (1) Children who have had Hib meningitis will perform less well on testing and will show more frequent problems at home and school compared to their siblings. (2) Medical and social variables will be predictive of sequelae. (3) Sequelae will increase with age and will be more frequent among older cohorts of post-meningitis children than among younger cohorts.